If I get chance I will do just that tomorrow . More interesting than the work I have lined up. What kind of music do you listen to?
@tommyst OK- listened to both. Totally unscientific subjective impressions- one dac feeding 2 amps simultaneously (a THX 789 for the Clear, balanced and the Topping L30 for the 1990s so both measured as transparent)- volumes not "matched" by measurements , but in the same ballpark by listening. All EQ disabled. Warning, I am rubbish at describing sound. And this is comparing the 2 noting areas of difference, rather than trying to review either. DT1990 had the A (analytical) pads
IMO its not a fair fight- the Clears just sound better. Far better separation of instruments. More balanced sound.
Both are comfortable to wear, very well built but you notice the Clear weight more. I have had them a month or so and never had neck ache from headphones before them. I do now.
I got the 1990 from Amazon warehouse for around £300 ages ago and the Clear from ebay £800 (so still 3x as much used as new). At those prices I consider the Clear just about acceptable- but not at RRP- no HP is worth that. Its not 3x as good, of course. Look at it another way. If you shopped around you could get an older Sennheiser HD800 and a 1990 second hand for about the price of a used Clear which would be a better buy. If you had 4 ears.
Subject to EQ on the 1990, they are both good headphones, but the Clear is superior. Is my 2 cents.